Method of stoking furnaces



Filed June 1s, 1932 4 Sheets-Sheet 1 re 3/ jzji Hal Jan. 14; 1936. H L, RAEFT 2,027,485

'METHOD OF STOKINQG FURNACES Filed June 18, 1932 4 Sheets-Sheet 2 Jan. 14, 1936. L. KRAEFT METHOD OF STOKING FURNACES Filed June 18, 1952 4 Sheets-Sheet 5 MW mw Jan. 14, 1936.

H. L. KRAEFT METHOD OF STOKING FURNACES Filed June 18, 1952 4 Sheets-Shet 4 Patented Jan. 14, 1936 UNITED STATES 2,027,485 r METHOD or STORING FURNACES Herman L. Kraeft, Cleveland, Ohio, ass lgnor to Murray-Ohio Manufacturing Company, Cleveland, Ohio, a corporation of Ohio Application June 18,1932, Serial No. 617,977

6 Claims.

stoking furnaces and is directed particularly to overfeed stoking of d omestic heating furnaces and has'for an object the provision of a coal stoking method whichwill 'be readily adaptable to use with various types of domestic furnaces, and which will be efliciently active with the functionings of thermostatic controls and whereby eiilcient combustion will be obtain Various types 'of coal stokersflhave beenprogardless'of the variation in design of the furnace housing and dimensional variations in the fire boxes of such furnaces.

Furthermore, the invention has been devel-' 'opedto meet widely varying conditions in the handling of diiferentkinds of coal .and regard-,

less of the degree of dryness or dampness of such coal. The invention has been used in connection with a stoker mechanism,- which may be brought into cooperative relation with a furnace structure without necessitating any serious alteration of the furnace structure at the time of installation, and the nature of the method is such that the fuel will be evenly spread upon the fire bed Without causing excessive dust or uncombusted gases to escape up the furnace flue, all of which I accomplish while avoiding fire hazards.

My method of feeding the fuel while fulfilling the foregoing stated purposes is to agitate a 3 substantially large supply of the fuel by revolving the fuel to cause the pile of fuel to settle downwardly,- whereupon I remove relatively small amounts of the fuel from the settling pile a by shifting such amounts in a substantially horizontal direction toward the fire bed, and

This invention is concerned with methods of agitate the finer pmticles of the fuel during such spreading action.

Further objects and purposes of my invention will hereinafter become apparent from the following description which sets forth the method when placed in use bythe utilization of stoker mechanism disclosed in the drawings hereof.

In the drawings Fig. 1 is a side elevational view of a domestic heating furnace of the hotair type showing my stoker mechanism asso-, ciated therewith; Fig. 2 is a perspective view of the stoker mechanism when not associated with the fire door of the heating furnace; Fig. .3 is an enlarged front elevation of part of the furnace and stoker mechanism-shown in Fig. 1; 5

. Fig. 4 is a fragmentary cross sectional elevation taken substantially through part of the stoker mechanism when the same'is .in cooperative relation with the fire door of the furnace and along the line 4-4 of Fig. 3; Fig. 5 is a cross sectional plan view taken through part of the stoker mechanism and substantially along the line H of Fig. 4.

. My invention will be described as being carried out by the mechanism illustrated in the drawings which mechanism comprises a unitary stoker mechanism which may be suspended upon an overhead trolley, whereby the fuel discharge end of the stoker mechanism may be inserted in the fire door of the furnace or withdrawn therefrom by shifting the stoker mechanism along the trolley rail which supports the same. The stoker mechanism is provided with a revolving hopper of a. substantial size, whereby a sufficient mass of fuel may be charged into the stoker mechanism to provide for about a twelve-hour fuel demand of the furnace during the very cold seasons.

In association with the hopper mechanism and disposed immediately therebeneath is a re- 40 ciprocating plunger, disposed within a substantially horizontally extending feed conduit or tube, preferably rectangular in cross section. The plunger is reciprocated by a crank shaft and pitman mechanism. which is preferably driven by a speed reduction means and the oscillating reciprocation of the connecting rod or pitman serves also as a'power source for causing the discharge end'thereof a revolving fuel flip- Y ping mechanism of definite design and having a definite relationship to an adjustable ledge,

associated with the inner end-of the feed tube.

whereby the flipping action can be varied depending upon the physicalcharacteristics of the particular fuel which is to be burned and the shape and area of the furnace grate. I also incorporate in the stoker -mechanism a blower mechanism which is suitably associated with the ash pit of the furnace, whereby when the thermal controls function to cause operation of the.

stoker mechanism, a modified forced draft may be applied to the underside of the fire bed.

The foregoingfoutlined stoker mechanism will now be described in detail.

In Fig. 1, I show a hot-air furnace I0, provided with the usual flre door frame flre pot I2 and ash pit l3. The stoker mechanism comprises a substantially large coniform hopper.

member l5, which is revolubly mounted upon a downwardly extending coal guiding chute in the form of a neck member l5, which, inthe present design, comprises a-base which supports the hopper I5 ,with the axis thereof oblique to a' horizontal and vertical plane. The base member I6 is round at the top and rectangular shaped at the bottom, and comprises a connecting passageway between the bottom opening of the hopper l5 and a rectangularly shaped fuel feeding tube 45, attached to the bottom of the member Hi. The base member l6 (see Figs. 1, 3

trolley member 23, by adjustable bolt members- 24 and 25, respectively. The trolley member 23,

is provided with upwardly extending trolley wheel brackets 26 and 21, bearing suitable wheels 28, which ride upon the trolley .rail 30.

The trolley rail may comprise a strip of standard angle iron, and the angle iron. 3|! is attached to rafters or' floor beams 3| by any suitable means, such as straps or brackets 32 and 33 (see Figs. 1 and 2). I prefer to mount the trolley rail 30 in such manner that the bracket member 32 will suspend the inner end of'the rail 30 slightly below the opposite end 'of the rail, whereby the rail slopestoward the furnace; thus causing the stoker mechanism to have a tendency to remain in a forward cooperating position relative to theme box door of the furnace.

The lower end of the'ho'pper mechanism is provided with an annular, outwardly flanged member 35, spaced a slight distance above the flange on the member I! and which comprises both a bearing plate for the lower end of the hopper and part of -the'mechanism, which causes intermittently revolving movement of the hopper.

The hopper is mounted upon rollers or spools to reduce friction, and, as shown in Fig. 3, I provide bearing spools or wheels 31 and 38, which are shaped to engage the flange of the member 35, and two similar bearing spools- 39 and 40. These four roller members are spaced substantially degrees apart and are supported by the flange member II. "The four members are respectively mounted upon boltFstuds 31a, 38a, 39a and 40a, which studs also serve to rigidly secure the lower ends of the strap members 22 and the bar members l8 and 8a, to the flange of the member The fuel feeding mechanism comprises the rectangularly formed tube 45, which is attached to and supported by the base member IS in any suitable manner. ,Disposed within the outer end of the tube and slidably arranged therein is a rectangularly formed plunger member 46, which is disposed to rest immediately beneath the outer edges of the bottom of the hopper and the base member l5, whereby an unrestricted passageway is provided between the base member l5 and the top of the tube 45 throughout substantially the entire width and breadth of the bottom of the member IS. The plunger member 45 is provided with a suitable bracket 48,

which carries a-wrist pin 49, the wrist pin serv- 1 ing to engage the inner end of a fork shaped connecting rod or pitman 50. The outer end of the connecting rod 50 is operatively attached to a crank pin 5| carried by rotatable disc 52, the disc bing mounted upon the 'end of a gear shaft 53,

whereby rotation of the shaft 53 will cause a reciprocating movement of the plunger 46 within the feed tube 45, and the travel of the plunger is dependent upon the radial displacement of the crank pin 5|, relative to the center of the shaft 53. The shaft 53 comprises part of a gear reduction mechanism housed within a casing 54,

the'casing being attached to the outer end of the feed tube 45.

' relative to the center of the shaft 53 to vary the stroke of the plunger, is afforded by the fact that the crank pin has the crank end thereof eccentrically formed.

It should be noted in Fig. 4, that thepin 5| is provided with an enlarged eccentric head 56 which coacts with the connecting rod 52. Hence, by adjusting the position of such head relative to the crank, the reciprocating movement of the plunger 46 may be varied as desired. In the present instance, the stroke of the plunger may be varied to be any distance between one inch and one and one-half inches. I provide means for preventing fuel dust from accumulating between the plunger and'tube.

In Fig. 4 in cross-section is shown a tray member. 58, which is slidably supported by transversely disposed plate members 59 beneath a slot 60 .formed in the'bottom wall of the feed tube 45. to extend substantially acrossthe bottom' thereof at a location immediately adjacent the outer edge 45a of the'lower part of'the plunger structure, whereby any-coal dust which becomes lodged along the side and bottom walls of the plunger will be permitted to escape into the tray. '58 and the slidable mounting of the tray permits. removal of such dust from time to time.

I arrangeat the forward fuel engaging face of the plunger 46 a fuel agitator means which rides along the bottom wall of the. fuel feed tube 45 substantially the fuel conducting length thereof, and this means may be in the form of a metallic strip 80, provided with a series of transverse strips 8|, shaped to comprise sub- '.stantially ratchet teeth, whereby upon the forfrom 8 inches by inches in height to consid-' tendency to move the coal rearwardly upon the return stroke of the plunger. The mechanism for rotating the hopper will now be described.

The hopper I5 is revolved by means of a pawl 84, pivotally attached at its outer, end to a bracket member 85, rigidly secured to the connecting rod 50 at such operative position that 'the pawl 84 may extend upwardly and out wardlyto engage, in step by step movements, within openings 35a, equidistantly spaced and formed in the'annular flange of the member 35. It will be apparent from Figs. 3 and 4 that revolving motion is imparted to the hopper during the return stroke of the plunger; thus voids momentarily created in the feed tube 45 by reason of the forward fuel feeding strokeof the plunger will be caused to be filled by reason of the agitation of the body of the fuel upon the return stroke of the plunger. A retaining pawl in'g and the proportioning and design of the flipper mechanism .are such that large particles of fuel cannot become lodged in any part of the mechanism which is exposed to the heat of the fire. This arrangement is also such that the stoker mechanism is readily adaptable to various sizes of fire door frames, which fire door frames vary from 9 to.I5 inches in width and erably greater dimensions. The mounting of the flipper housing is such that regardless of the width of the fire door frame of the furnace, the-rotary flipper member can always be adjusted to a juxtaposed position relative to the fire bed edge.

This fuel flipper mechanism comprises a revolving cylinder I0 (see Fig. 4), mounted upon a shaft 12. The shaft 12 may have a multistep pulley 13 mounted on an extendirg end thereof, which pulley;may be driven by a belt I4 (see Fig. 3). The belt is driven by a pulley 11, mounted upon one end of the shaft 53. The

cylinder "I0 is of substantially the same length I as the width of the fuel feed tube 45 and the surface design thereof is ofa particular functioning shape to be described in greater detail hereinafter, and is provided with an enclosing casing comprising an arcuately formed member 14, having end walls 15 to which are at- .ta'ched suitable bearing members I6 for rotatmember being secured to a, door closure plate formed of any suitable material such a slab of asbestos board 92, which may be of such dimension as to comprise a closure for the largest size doors to be found on domestic furnaces of whatever type; The side walls 15 are suitably flanged, as indicated at 06 (see 5) within a housing, I

for rigid attachment to the housing member 90, and the width and height of the housing member 90 are such as to provide suflicient, space for the enclosure of the pulley member 15, as well as the bearing members 16." The side walls I5 extend upwardly and are attached to a top member 91, which is flanged at the outer edge thereof for attachment to the box-shaped housing member 90 as shown at 98 (see Fig. 4). The member 91 is of a stepped-down formation to serve as a fuel guide or deflector to deflect downwardly any heavier particles of fuel which might be flipped upwardly at too great an angle to escape the inner edge 99 of the fire door frame, and the outer portion 9Ia thereof engages the top outer surface of an extension tube I00, which comprises the inner portion of the fuel feed tube 45. The top wall 90a of the box-like member 90 extends between the portion 910 and the' top wall Slaof the telescoping housing member 9|. The tube I00 is shaped to telescopically embrace the outer surfaces of the inner end of the tube 45, whereby the tube I00 may be of any desired length. to suit the particular requirements of the installation. I provide securing means in the form of binding bolts IOI for securing the tube I00 firmly tothe inner end of the tube 45. I also provide binding lugs and nuts, as indicated at I02 upon the housing member 90, and slots I04 and I05 are respectively provided, whereby the lugs may extend therethrough and clamp the housing members 90 and 9| firmly together in any desired adjusted position. v

I also provide an adjustable horizontally dispose'd ledge member I I0, which in function comprises an extension of the bottom wall of the fuel feed tube,'comprising the members 45 and I00, and which serves to predetermine the falling movement of the 'coal particles as the same escape thereover upon the revolving flipper cylinder 10, and this member IIII may be of a suitable design to be disposed immediately between the uppermost path of rotating movement of the member I0 and the bottom wall of the fuel feeding tube, and, as shown in Fig. 4; the member H0 is provided with downwardly extending slotted flanges HM, and a clamping bolt III of any convenient design may extend through the slots in the flanges, whereby the member I I0 can be secured in any desired adjusted position. Graduations, as indicated at II2 may be provided on one of the side walls I5 to indicate to the adjustor the degree of adjustment of the ledge member IIO, relative to a verticalplane extending through the axis of the flipper frame I0.

In order to eliminate the necessity for the use of damper motor controls, ,I provide a blower mechanism, which may be operated only when the stoker mechanism is functioning to feed fuel to the fire bed. This blower mechanism may comprise the conventional type of blower casing I and an impeller I2I, the casing I20 being secured to the casing of the power motor I23, and the impeller I2I being suitably secured 'to one end of the motor shaft I24. Depending from the blower casing I20 is aflexible tube I25, which may extend downwardly to the ashthread mounting upon a threaded stud I82, carried by the blower casing. Adjustment of the volume of air is obtained by moving the disc I8I axially toward or away from the openings I80 in the casing I20. The volume of air required is determined by the size of the fire bed, the burning characteristics of the fuel to be used and the heat delivery demands made upon the furnace by the thermostatic controls. Hence, adjustment of the disc I8I relative to the air inlet opening of the blower casing will be determined .by operatingtrials of the stoker mechanism at the time of installing the same.

The motor I23 may be suitably mounted in aninverted position upon "'a bracket member I28, adjustably secured by bolts I29 to a depending bracket member I30, secured to the bottom wall of the fuel feed tube at a convenient position to permit practical driving connections between the pulley I32 mounted upon one'end of the motor shaft I24 and pulley I33, mounted upon the shaft of the gear reduction mechanism. A suitable belt I34 serves to drivingly connect the pulleys I32 and I33. from Fig. 3 that various speed selections may be made by reason of the provision of step pulleys I3, I1, I32 and I33, respectively mounted upon the flipper cylinder shaft, on the gear reduction shaft, and motor shaft.

It should be noted that the relationship of the rotatable flipper member 10 relative to the inner discharge end of the fuel feed tube and to the rim of the fire pit is such that the desired flipping action on the fuel particles can be obtained without causing undue agitation of the fuel particles. The plunger makes from 1 to 3 strokes per minute and the fuel displacement along the tube is from 1 inch to 1 inches per plunger stroke. is such that it can be disposed immediately beneath and adjacent to the discharge end of the tube and also can be disposed in such position that the flipping aotion thereof will not cause the coal particles 0 be thrown too violently.

The dimensions of the tube in cross-section are approximately 4 inches high and 6 inches wide and the flipmr member extends the full width to about 900 R. P. M; and the correct speed will be dependent upon the size of the flre bedand the physical characteristics of the fuel to be fed thereto.

The surface of the flipping member 10, as shown in the drawings, comprises veins or blades 10a, preferably integrally formed about the perimeter of the flipper member to taper toward the center thereof, thusimparting to' the fuel particles not only an outward throw from the discharge end of the: tube, but also an angular throw relative to the tube center line. I also form the surface 10b of the rotatable member, as shown in Fig. 4, in such-mannerthat at such times as the stoker mechanism is at rest any coal particles, which may drop from the inner end of the tube cannot become lodged within- It will thus be apparent- The size of the rotatable member-10 able disc-shaped member I8I which has a screw.

are there any fuel particles exposed to the heat of the fire bed, which particles could in any way become ignited and thus cause the ignition of the fuel which is at rest within the feed tube.

My prior experimenting with stokers of the overfeed type has disclosed that a feed tube carrying fuel cannot be extended into the fire box without the attendant difficulties. Under such a condition, the fuel when in the tube has a tendency to coke, thus liberating tar and other sticky-components of the average fuel. Likewise, there is always'present a flre hazard under.

such circumstances. It will be apparent from the design disclosed in the drawings that my method of overfeed stoking of a furnace can be.

successfully performed on different types of domestic heating furnaces while the diificulties and dangers above mentioned are avoided.

Likewise, the design discloses a practical form from a commercial viewpoint, in that regardless of variations in the width of the fire door frame II, the inner end of the tube and the flipper mechanism can'always be adjusted to the proper relationship relative to the rim of the fire pit by reason of theteles'copirig construction of the flipper housing and by reason of the fact that I provide the fuel feeding tube 45 with the extension tube I00, thus making theinstallation of the stoker mechanism readily adaptable to various furnace structures.

My method has been applied to anthracite fuel of the so-called pea-size, as well as to anthracite culm and bituminous slack coals of trol devices now on the market.

I am aware that flipper mechanisms for throwing coal onto a fire bed have been proposed heretofore. Such mechanisms have usually been associated with some form of blower means functioning through the flre door. I have devised a flipper mechanism which avoids the use of a blower and I thus avoid the escaping of partially burnt coal dust up the chimney. Protractedtesting of my stoker demonstrates the importance of agitating the mass of fuel while removing measured quantities thereof and the ledge principle of fuel escape makes thecontrolling of the flipping action practical, whereby the powdered portion'of the fuel'will not be unduly agitated to the extent that the same would be caused to escape up the flue without being burned. The apparatus has been quite successful in stoking a variety of fuels,'while maintaining a proper flre bed that will produce very low ash and low fuel losses.

I claim:

1. The method of feeding fuel to a fire bed, comprising intermittently revolving a mass of fuel on an axis disposed obliquely to both vertical and horizontal planes while permitting part of the mass to gradually escape at the bottom thereof, shifting that part of the fuel which has escaped from the revolving mass in a substantially horizontal direction toward the fire bed during the period when the revolving mass is at rest and finally imparting to the fuel particles 9. fiipped movement to cause the fuel particles to be spread over the fire bed.

2. The method of feeding fuel to a fire bed, comprising intermittently revolving a mass of fuel about an axis whilepermitting part of the mass of fuel to gradually escape at the bottom of the mass, intermittently shifting that part of the fuel which has escaped fromithe revolving mass in a substantially horizontal direction toward the fire bed while the revolving mass is stationary, and finally imparting to the fuel particles a flipped movement to cause the fuel particles to be spread over the fire bed.

3. The method of feeding fuel to a fire bed, comprising revolving a mass of fuel on an axis disposed obliquely to both vertical and horizontal planes while permitting part of the mass to gradually escape at the bottom thereof, shifting that part of the fuel which has escaped from the revolving mass in a substantially horizontal direction toward the fire bed to effect a falling movement of the fuel particles in a region adjacent the fire bed edge and finally imparting to the fuel particles as they are thus falling a flipped movement to cause the fuel particles to be spread over the fire bed.

4. The method of feeding fuel to a fire bed, comprising revolving an entire mass of fuel on an axis disposed obliquely to both vertical and horizontal planes, shifting the lowermost part of the downwardly moved part of the mass of fuel in a substantially horizontal direction toward the fire bed while permitting part of the shifted I fuel as it is being shifted to drop vertically ad jacent the boundary line of the fire bed and imparting to the fuel particles as they are thus 5 falling a flipped movement, whereby the fuel is caused to be spread over the fire bed.

5. The method of feeding fuel to a fire bed, comprising revolving an entire mass of fuel on an axis disposed obliquely to both vertical and 1 horizontal planes, shifting the lowermost part of the mass of fuel in a substantially straight line horizontal direction toward the fire bed, permitting part of the fuel as it is thus shifted to escape by a falling movement adjacent to and 15 toward the boundary line of the fire bed and imparting to the fuel particles as they are escaping a flipped movement, whereby the fuel is caused to be spread over the fire bed.

6. The method of feeding fuel to a fire bed. 20 comprising revolving a mass of fuel on an'axis disposed obliquely 'to both vertical and horizontal planes, shifting the lowermost part of the mass of fuel in a substantially straight line direction. toward the fire bed to cause part of the fuel as 25 it is thus shifted to escape with a falling movement adjacent to and toward the boundary line of the fire bed and imparting to the fuel particles as they are escaping a flipping action, whereby the escaping fuel is caused to be spread over the 30 fire bed.

HERMAN L. KRAEFT. 

